Variable-reactance transformer



H. L, COLE ET AL VARIABLE REACTANCE TRANSFORMER Filed Fb. 14I

Xqleg/Mm Fl' Z. 4-7 if! l 521 50/ 56' Aug. 23, 1932.

777a\79 INVENTORS.

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WITNESSES ATTORNEY im l y;

Patented Aug. 23, 1932 UNITED VSTATES PATENT OFFICE f HORACE L. COLE, 0F SHARON, AND HOHER H. WAGNER, OF PITTSBURGH, PENNSYL- VANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC & MANUFACTULIING COMPANY, A y

CORPORATION OF PENNSYLVANIA VARIABLE-REACTANCE TRANSFORMER Application nled February 14, 1931.

Our invention relates to transformers and more particularly to the provision of transformers having a plurality of reactance values at the same voltage and power rating.

Heretofore, in meeting the demand for transformers which have two or more values of reactance at the same rating, the practice has been to use one or more separate reactors mounted either' in the same tank as the main transformer or externally and arranged to be connected in series with one of the main windings when the higher reactance values are desired. It will be apparent that such an arrangement is subject to the disadvantage of requiring the additional reactor apparatus, which, it will he appreciated, increases the total cost, complicates the connection, requires added space and reduces, when in circuit, the over-all operating eiliciency of the equipment, because of the losses which occur in the reactor materials.

lVe have discovered that, by designing the main transformer with one or more extra coils suitably7 positioned in the winding assemblies, different values of reactance may be obtained merely by shifting the connections to give various combinations of active or incircuit coil grouping. By the use of this principle, we are able to construct a selfcontained multi-reactance transformer which is much less expensive than an equivalent transformer equipment using separate reactors and only slightly more expensive than a singlereactance transformer of comparable rating.

Broadly stated, an object of our invention is to provide a transformer adaptable, entirely Within itself, for use under several different operating conditions, each of which requires a different reactance value.

More specifically, it is an object of our in' vention to provide, in a` transformer, a plurality of winding arrangements having differ,- ent reactance values, different connections of which may be selected at the will of an operator.

Another object of our invention is to increase the efficiency of transformer equipments which are used in services requiring a plurality of reactance values.

Serlal No. 515,702.

Figure 1 is a view, in sectional elevation, of a transformer in. which the coils are arranged, in accordance with our invention, to provide two different reactance values for the transformer and Figs. 2 and 3 are similarviews of transformers showing other arrangements of the individual coils of the interleaved windings which provide a plurality of reactance values, two for the transformer of Fig. 2 and three for the transformer of Fig. 3f

Referring to the drawing, particularlv Fig. 1, we have illustrated a transformer 10 'of the interleaved-coil type, on the central leg of the core'll of which are placed the individual coils which comprise two separate windings.

One of the windings includes the individual coils in the central group 12, interconnected in the usual manner, as shown, the winding connections being brought out by leads 13 and 14, thru which the Winding may be connected to some external circuit (not illustrated). The second Winding includes the individual coils in the two outside groups which include, respectively, coils 15, 16 and 17 in the first and coils 18, 19 and 20 in the second. Connections from lthis winding are brought out through leads 21 and 22. Provision for adjusting the reactance value of the last named winding is made in a manner to be explained.

It will be recognized 'that the transformer illustrated in Fig. l is of a known design which employs the interleaving principle to reduce the total reactance of the windings by shorteningr the path and decreasing the intensity of the leakage flux. As is Well known, windings having a large number of interleavings give a much lower reactance to the trai'isiormer than windings having only a few interleaved coil groups.

. lt will further be apparent that the respective reactance values ot the individual coils in the groups mentioned are not all the same, even though the coils themselves have the same number ot turns and are of identical design in all respects, since, as is known, the reactanf-e of any given coil is a function of the length of the path and the intensity of the leakage flux affecting that coil, which quantities depend. in the present instince, upon the position which the coil occupies in the interleaving sclieme.

As the indiridual coil reactances, produced by such lines of magnetic flux as link, and are common to, the one winding only, collectively comprise the total reactance of the transformer, it will be evident that, when the coils oi" the one winding are most remotely separated from the coils of the other winding, the transformer will have the highest reactance value, since, in auch an arrangement, the leakage fluxis greatest. Thus, in the transformer illustrated, coils 15 and Q0, because of their positions, are capable of giving a higher reactance to the transformer than the identicall;T designed coils 17 and 18, since they are farthest removed from the section of the other winding.

To obtain the two values of reactance in the transformer of Fig. 1, we provide, in the winding which includes the two outer sections mentioned, six similar coils positioned as shown and of such dimensions and number of turns that only tive of the six are required for connection in the circuit to give the desired ratio ot voltage transformation. le include switching means for selecting, at will, the extra or inactive coil as one which, by its position, produces a high reactance or which gives alowerreactance. The remaining five coils in the circuit wlll thereby give, respectively, the lower or the higher value for the total winding reactance.

The switching means mentioned maf,1 be of any suitable type, such as a terminal board having studs and movable connection links or equivalent knife switches, as we have represented at 23 and 24, in Fig. 1.

in the scheme of connection shown, the higher value of reactance for the transformer is obtained, when switches 23 and 24 are closed to the upward position, in which case, the circuit thru the adjustable reactance winding extends from lead 2l, through switch 23, conductor 25, coils 15 and 17, conductor 26, switch 24, conductor 27, coil 19 and coil 20, to lead In this combination, the. inactive or extra coil is coil 18, which produces less reactance, as previously explained, than the alternate coil connected in the active circuit or coil 15 which produces a higher reactn e ance. Therefore, the total reactance of the.

winding and of the transformer, is of the higher value.

To obtain the lower value of reactance, switches 2:3 and 24 may be closed to the downward position, in which case, the circuit through the adjustable rcactanee winding extends from lead E21, through switch 225, conductor coils ll and 1T, conductor 2li, switch 2l, conductor 2S) and coils 18, lll and 20, to lead It will be seen that, in this combination, coil 18, which is in closer position with respect to the coils in group 12, has been substituted for coil l5, which is more remote from the coils in group 12, and the total reactance of the winding has` thereby been lowered.

In Fig. 2, we have illustrated a transform er having a larger number of individual coils inthe two windings than that ot Fig. 1 but which lends itself equally well to the utilization of our invention. One of the windings, terminating in leads 30 andl, is of the usual constant-rcactance type and comprises the two coil groups 3Q and 323, as shown. The other winding, terminating in leads 3l and 35, incorporates our ad justubiereactancc principle and comprises the remaining three groups of coils, the first groups including coils 34, 35, 36 and 3T, the .secoinl group coils 38, 39, :l0 and 41 and the third group 412, 43, 4l and 45. As in the traus't'oinier oi Fig. 1, the coils of this last rained winding arc f ll similar, and, further, thev are so lcsigned that only eight of the total twelve are required for connection in thel windingA circuit to give the desired ratio of transforma"ion.

For effecting rif-arrangcnicnts o' active coil groupings, we provide the switches lo, 4'( and 48. It will be understood, however, that suitable switching means of any other type, such as terminal-board connectors or tap changers, may be used with equal success.

To obtain the higher value ot reactancc in the last-Lamed transformer winding, switches 46, Ll? and 48, are, as in the case of F ig. 1, closed to the upward position. The circuit through the windingcxtends from lead 34, through switch iti, conductm' la, coils 34, 35, 86 and 3T, conductor F20. left blade of switch 47, conductor 51, right bladtA of switch 47, conduct-or 52, coils 42, 13, 4l and 45, conductor' and switch 18, to lead 35. 1t is seen that, for this combination, the central grou) of coils, 38, 39, #l0 and 41 is inactive, an since the.,v are between, and in close proximity to coil groups 32 and. 3S of the other winding, their combined reactance is lower than that of coils 34, 4.1 and which are included in the circuit, these last named coils, as will be noted, being more remotely separated from coil groups 32 and 33.

The low reactanee value tor the transformer of Fig. 2 is obtained when switches 16, 47 and 48 are all closed to the downward position. The winding circuit lthen extends from lead 34, through switch 46, conductor 54,

coils 36 and 37, conductor 50, lett blade of' switch 47, conductor 55,'y coils 38, 39, 40 and 41, conductor 56, right blade of switch 47, conductor 52, coils 42 and 43 conductor 58 and switch 48, to lead 35. It will be seen that, in this set-up, coils 38, 39, 40 and 41 have been substituted in the active circuit for coils 34, 35, 44 and 45. This connection increased the interleavin of the two windings, which, as explained before considerabl f reduces the total reactance. 11n addition, t e first named coils are of a higher reactance, as has been explained, hence, the reactance of the transformer has thus been lowered by this means as well.

Fig. 3 iilustrates our invention as applied to a transfo: ner in such manner that three di tfcrent reactance values are obtainable. lThe transformer comprises the usual core 10 and associated coils interleaved and connected to constitute two separate windings. One winding, which terminates in leads 59 and 60, is made up of the three coil groups 61 and 62 and 63, connected in the usual manner, as shown. The other winding, which terminates in leads 64 and 65, includes the remaining four groups of coils comprisin respectively, coils 66, 67 and 68 for the rst, coils 69, 70, 71 and 72 for the second, coils 73,74, 75 and 76 for the third and coils 77,78 and 79 for the fourth.

As in the transformers of Figs. 1 and 2, the coils of the last named winding1 are all similar, they being so designed t at only twelve of the total fourteen are required for connection in the Winding circuit to give the desired ratio of transformation. To effect the necessary changes in active coil groupin of this last named winding, we have rovide suitable switching means, illustrat as four knife switches 80, 81, 82 and 83.

The highest value of reactance is obtained, 4

in the scheme of Fig. 3, when all of the switches are closed to the upward position. The circuit through the adjustable reactance winding then extend from lead 64 through switch 80, conductor 84, coils`66, 67 and 68,

75, conductor 88, switch 82, conductor 89, coils 77, '78 and 79, conductor 90 and switch 83 to lead 65.

for the transformer, switches 8O and 81 are closed to the downward position, and switches, 82 and 83 are closed to the upward position. The circuit through the adjustable winding then, extends from lead 64, through switch 80, conductor 91, coils 67 and 68, conductor 85, switch 81, conductor 92, coils 67, 68, conductor 85, switch 81, coils 70, 71 and 72, conductor 87, coils 73, 74 and 75, conductor 55 88, switch 82, conductor 89, coils 77, 78 and conductor 85, switch 81, conductor 86, coils 70, 71 and 72, conductor 8 7, coils 73, `74 and- 79, conductor 90 and switch 83, to lead 65. It can be seen that coil 69 has, in this combination, bf en substituted in the active circuit for coil 66 of a higher reactance and, therefore, the total reactance of the winding has been lowered to an intermediate value.

VThe medium value of transformer reactance may also be obtained by closing switches and 81 to the upward position, and switches 82 and 83 to the downward position, in which case, the adjustable-winding circuit extends from lead 64; through switch 80, conductor 84, coils 66, 67 and 68, conductor 85, switch 81, conductor 86, coils 7 0, 71 and 72, conductor 87, coils 73, 74, 75 and 76, conductor 93, switch 82, conductor 89, coils 77 and 78, conductor 94 and switch 83, to lead 65.

To obtain the low reactance of the winding, all ofthe four switches may be closed to the downward position, in which case, the circuit through the adjustable winding extends from lead 64, through switch 80, conductor 91, coils 67 and 68, conductor 8,5, switch 81, conductor 92, coils 69, 70, 7l and 72, conductor 87, coils 73, 74, 75 and 7 6, conductor 93, switch 82, conductor 89, coils 77 and 78,

conductor 94 and switch 83, to lead 65. In I this case, coil 76 has b'een substituted in the active circuit for coil'7 9, which is of higher reactanoe, therefore, the total reactance of the winding has'been reduced to the low value.

In the examples which have been illustrated and explained, the-reactance 'change has been affected by a change of grouping of the active coils lin the circuit of one winding only. It will be understood, however, that similar shiftin provisions can, if desired, be made in both ogthe windings of a transformer, in the case of the two-winding types, or in any or all of the windingsin transformers having more than two windings. Likewise, core structures of types other than the one which we have shown may be used in transforners employing our multi-reactance princ1 e.

t is believed that` the specific embodiments, which we have shown in Figs. 1, 2 and 3, will be sufficient to illustrate that, by using a still larger number of extra coils, combined with suitable interleavinrr and switching means, number of different reactance values may be obtainable in a transformer constructed in accordance with our invention. It will be To obtain the medium value of reactance v,

practically any ydesired tion, therefore is not to be restricted except l insofar as is necessitated by the by the spirit of the appended claims.

prior art and n..

`We claim as our invention:

1. A transformer comprising a core of magnetic material and windings for separate electrical circuits placed upon said core, the wind* ing for each circuit comprising groups of coils interleaved with coil groups of the other circuits, certain of said coils in one or more of the winding assemblies being so positioned in the interleaving scheme as to have differentI inherent reactances, and switching means whereby one or more extra coils of high reactance may be substituted in the active-wind ing/circuit for one or more similar coils of lower reactance to thereby eti'ect a change in the reactance of the transformer without materially changing the ratio of voltage transformation,

2. A. transformer comprising, in combination, a core ot magnetic material, and windings for one or more separate circuits placed upon said core, the winding for each circuit comprising one or more groups of coils interleaved with similar coil groups of the other windings, certain coils ot similar design in one or more of the winding assemblies being so positioned in the interleaving scheme as to be acted upon by different values of leakage flux to thereby have dilerent values of inherent reactance, and switching means whereby one or more coils of high reactance may, at will, be substituted in the active circuit for one or more coils of lower reactance to thereby eect a change in the reactance of the transformer without materially changing the ratio of voltage transformation.

3. A transformer comprising, in combination, a core of magnetic material, and windings for one or more separate circuits` placed upon said core, said winding for each circuit comprising one or more groups ot coils interleaved with coil groups of the other windings, certain coils of similar design in one or more ot the winding assemblies being so positioned in the interleaving scheme as to have different reactance values. those coils of high reactance being more remotely separated from coil groups ot the other windings than coils of lower reactance, and switching means whereby one or more coils of high reactance may, at will, he substituted in the active-winding eircuit for one or more coils of lower reactance to thereby eiiect a change in the eifective reaetance ofthe transformer without materially changing the ratio ot voltage transforn'iation.

4. In a. transformer comprising a core of magnetic material. ha ving a plurality of windings for separate electrical circuits disposed thereon, each of said windings comprising groups oi coils interleaved with coil groups of the other windings, the arrangement being such that coils in certain positions in the interleaving scheine are acted upon by greater values ot leakage flux than are coils in certain other positions so that the coils first-named have higher reactances than do those last- ISG 

